Food Synergy: The Key to Balancing the Nutrition Research Effort

Article excerpt

INTRODUCTION

This paper contrasts strategies for conducting nutrition research that investigate the relationship between diet and disease. This research is the basis for public policy recommendations, notably advice about diet. Historically, nutrition research has focused on single substances, whether macronutrients, micronutrients, or the many other bioactive substances present in food. A more recent strategy focuses on food synergy, which is based on the assumption that in most cases the many substances in food have additive or more than additive effects on health.1-5

The position we take in this paper is that too great a focus on single nutrients or other bioactive substances will not significantly advance public health dietary advice, unless deficiency diseases are present. As a strategy for advancing nutrition science that informs this advice, a focus on single nutrients is unlikely to succeed because in the large majority of cases this research does not model the complex effects of food consumption on human biology. Even where simple additive effects of single substances may emerge and be important, it is very difficult to translate this knowledge to that relating to the consumption of whole foods and whole diets. A strategic approach that will prove more fruitful and better inform public health dietary advice is to focus on food and dietary patterns, within the concept we call food synergy.

The aim of this paper is to defend this position. First, the concepts of nutrient deficiency and food synergy are presented along with a brief summary of exemplary research that addresses the relationship between dietary patterns and disease. The concept of food synergy is then applied to the research context, with considerations for research designs, such as observational studies, randomized controlled trials (RCTs), or experiments in the basic sciences, with the assertion that correct inferences are most likely to be made based on convergent evidence from multiple perspectives. The conclusion focuses on lessons for research design which integrates the preceding appraisal.

NUTRIENT DEFICIENCY DISEASES: AN INFORMATIVE BUT LIMITED REFERENCE POINT

For several decades, roughly from the 1920s to the 1950s, nutrition science achieved great success in identifying the various vitamins and minerals in food and discovering their mode of action. This was made possible by clearly defining actions through the disciplines of biochemistry and physiology. In turn, a nutrient deficiency could be linked to specific symptoms. The deficiency disease could be prevented (and often reversed) by giving that nutrient in an isolated (pure) form.

It has been many years since any new essential nutrient has been discovered that explains the cause of a deficiency disease. However, the concept is still very much alive, though in a modified form. In recent years studies of single substances contained in food have led to promising advances in several areas of health. A noteworthy example of this is vitamin D. Much evidence suggests that suboptimal levels are widespread in many populations and that this significantly increases the risk for several disorders, including possibly cancer.6 However, not all observational epidemiologic studies show benefit from supplemental vitamin D.7 It may be that jumping into supplementation is not the correct or only response to the observation of increased risk associated with low vitamin D levels. A rational response would ask what else could the associations mean and whether there is a broader sphere of action that might need to be considered?

There are many other bioactive substances in food apart from micronutrients. It must be remembered, however, that our ability to discern whether food components are beneficial or harmful is likely to be related to the balance in the amount consumed. Prominent examples are as follows:

* The great majority of the population has an excessive intake of sodium and this is closely associated with hypertension8,9 and cardiovascular disease (CVD). …